1. Field of the Invention
The present invention generally relates to an ignition apparatus for an internal combustion engine. More specifically, the present invention is directed to such an apparatus that an instruction signal for an ignition operation to an ignition coil is produced from a control apparatus for executing an ignition control, and on the other hand, a monitor signal indicative of either a success or a failure of the ignition operation is returned from a circuit made with an ignition coil in an integral form to the control apparatus.
2. Description of the Related Art
Conventionally, as disclosed in Japanese patent application Laid-open (KOKAI DISCLOSURE) No. 64-35078, an arrangement has been proposed that a voltage of an ignition signal is used as a power supply so as to operate an igniter circuit. With employment of this arrangement, since a voltage-regulated output of the control apparatus can be used as the power supply of the igniter circuit, no longer a voltage regulating circuit is employed in the igniter circuit, so that the igniter circuit can be made compact and simple.
On the other hand, in order to determine a failure of an ignition system, it is desired to establish such a system capable of obtaining a monitor signal representative of a success or a failure of an ignition operation. Thus, the system has been proposed in, for instance, Japanese Patent Application Laid-open No. 63-25374, in which the signal for indicating whether or not the primary coil of the ignition coil is energized is returned from the igniter circuit to the control apparatus.
However, in the circuit as proposed in the above-described Japanese Patent Application Laid-open No. 63-25374, the igniter circuit should require an exclusively used power source so as to superimpose the monitor signal on the ignition signal line. As a consequence, there is such a problem that compactness of the circuit scale is incompatible with the response of the monitor signal, which are caused by that the ignition signal is used as the power source.
Also, to obtain monitor signals, many attempts have been made to detect the energizing conditions to the secondary coil of the ignition coil. However, the signal line connected to the secondary coil for producing the high voltage should be connected to the control apparatus. There is another problem of noise resistance characteristics in the case when the very small signal produced by indirectly detecting the energizing current of the secondary coil is deriven up to the control apparatus.
Furthermore, when the energizing condition of the secondary coil to produce the monitor signal, since the monitor signal is returned after the ignition signal is ended, such a problem exists that the monitor signal cannot be discriminated from the ignition signal.
On the other hand, as illustrated in FIG. 24 and FIG. 25, an ignition apparatus for a coil distribution type ignition system for internal combustion engine is conceived as a prior work which detects an occurrence of an ignition failure. FIG. 25 is a detailed circuit diagram for illustrating circuit blocks 200a and 200b of FIG. 24. FIGS. 26A to 26D are timing charts for representing signal waveforms appearing in various circuit portions of the circuit diagrams shown in FIG. 24 and FIG. 25. This ignition apparatus is so arranged that ignition signals IGt1 and IGt2 corresponding to ignition coils of the respective two cylinders are produced from an ECU 100 to the circuit blocks (coil circuits) 200a and 200b equal to a coil built in an igniter (namely, igniter is built in coil), and a monitor signal IGf is returned from the circuit blocks 200a and 200b to the ECU 100.
The ECU 100 is mainly comprised of a microcomputer (MC) 110, a reference power supply Vcc, and the same circuit blocks (current supply) 120a and 120b corresponding to the ignition coils of the respective two cylinders for the current supply. The circuit blocks 200a and 200b are mainly constructed of an input filter circuit 201 for performing an input signal process; a gate circuit 202; an ignition coil 203; a lock preventing circuit 204 for forcibly interrupting a primary current of this ignition coil 203 after a preselected time since the primary current of the ignition coil 203 is started to flow; a transistor 205 for causing the primary current of the ignition coil 203 to start to flow; an I1 detecting resistor 206 for detecting the energizing current I1 of the ignition coil 203; a constant current control circuit 207; an energizing current detecting circuit 208; a monitor signal (IGf) waveform shaping circuit 209; and a reference power supply Vcc.
In this ignition apparatus for the internal combustion engine, the terminal numbers 10 of the circuit blocks 200a and 200b are connected to each other in a halfway of the wiring line through which the monitor signal IGf is returned from the circuit blocks 200a and 200b to the ECU 100, and are connected to the terminal number 3 of the ECU 100, namely are wired-OR-connected to have a function as a signal line. As a result, a total number of wiring lines may be reduced.
Also, as shown in FIG. 27 and FIG. 28, it is also conceived such an ignition apparatus for the individual cylinder ignition system for internal combustion engine for detecting an occurrence of an ignition failure. FIG. 28 is a detailed circuit diagram for illustrating a circuit block 400 of FIG. 27. This ignition apparatus is so arranged that ignition signals IGt1, IGt2, IGt3 and IGt4 corresponding to ignition coils of the respective cylinders are produced from the ECU 300 to a circuit block (igniter) 400, and the monitor signal IGf is returned from the circuit block 400 to the ECU 300.
The ECU 300 is mainly comprised of a microcomputer 310, a reference power supply Vcc, and four same circuit blocks (C.S.) 320a, 320b, 320c and 320d corresponding to the ignition coils of the respective cylinders for the current supply. The circuit block 400 is mainly constructed of an input filter (I.F.) circuit 420 for performing an input signal process; a gate circuit (G) 430; circuit blocks 410a, 410b, 410c, 410d having the reference power supply Vcc; an I1 detecting resistor 401 for detecting the monitor signal IGf; a constant current control circuit 402; an IGf detecting circuit 403; a lock preventing circuit 404 for forcibly interrupting primary currents of the ignition coils 500a, 500b, 500c, 500d after a preselected time since the primary currents of these ignition coils are started to flow; and a reference power supply Vcc.
In this ignition apparatus for the internal combustion engine, both of the I1 detecting resistor 401 employed in the circuit block 400 and the emitters of the respective transistors connected to the terminal number 22 of the four same circuit blocks 410a, 410b, 410c, 410d are commonly connected to each other. As a result a total number of wiring lines for returning the monitor signal IGf to the ECU 300 can be reduced.
In accordance with the ignition apparatus for the internal combustion engine shown in FIG. 24, although this ignition apparatus employs a relatively simple structure, when such a system with no monitor signal IGf is arranged, unnecessary wiring lines are required so as to construct the system with no monitor signal.
On the other hand, in the ignition apparatus for the internal combustion engine as shown in FIG. 27, similar to FIG. 24, it is impossible to realize such an ignition apparatus having the signal line for the monitor signal IGf by employing the same number of wiring lines used in the ignition apparatus without the signal line for the monitor signal IGf.